Fluid Mechanics and Acoustics Laboratory - UMR 5509

LMFA - UMR 5509
Laboratoire de Mécanique des Fluides et d’Acoustique

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Home > Research Support > Scientific instrumentation > Techniques > ILIDS - Interferometric Laser Imaging for Droplet Sizing

ILIDS - Interferometric Laser Imaging for Droplet Sizing

This technique, also called IPI or IMI, paired with a PIV system, makes possible to measure the diameter of spherical transparent particles and two velocity components. The optical setup is identical to the one used with PIV. It is composed of a double cavity Nd:Yag laser generating two superposed laser sheets and of a PIV type camera. The camera is placed at a diffusion angle where the particles reflected beams have the same intensity than the refracted ones, that is at approximately an angle of 70° for water drops and a vertical polarization of the laser.

If the camera focus is perfect, we can observe two shiny points, called glory points. They match the impact points of the beams diffused by the particle in the camera direction.

If the focus is undone, the interference fringes appear. The size of the fringes depends on the level of defocusing and the number of fringes depends on the size of the particles and on the collection angle.

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Example of data analysis
Thesis D. Chareyron

Measurements tools:

- Several double cavity pulsed Nd:Yag lasers (see PIV section)
- Several double frames CCD cameras (see PIV section)
- A double cavity pulsed Nd:YLF laser (see TR-PIV section)
- Several CMOS fast cameras (see TR-PIV section)